Using DBMS_PROFILER

Overview

This package enables the collection of profiler (perfoprmance) data for performance improvement or for determining code coverage for PL/SQL applications. Application developers can use code coverage data to focus their incremental testing efforts.

With this interface, you can generate profiling information for all named library units that are executed in a session. The profiler gathers information at the PL/SQL virtual machine level. This information includes the total number of times each line has been executed, the total amount of time that has been spent executing that line, and the minimum and maximum times that have been spent on a particular execution of that line.

Note:

It is possible to infer the code coverage figures for PL/SQL units for which data has been collected.

The profiling information is stored in database tables. This enables querying on the data: you can build customizable reports (summary reports, hottest lines, code coverage data, and so on. And you can analyze the data.

Total time spent in this unit in nanoseconds. The profiler does not set this field, but it is provided for the convenience of analysis tools.

spare1

NUMBER

Unused

spare2

NUMBER

Unused

Table 64-3 Columns in Table PLSQL_PROFILER_DATA

Column

Datatype

Definition

runid

NUMBER

Primary key, unique (generated) run identifier

unit_number

NUMBER

Primary key, internally generated library unit number

line#

NUMBER

Primary key, not null, line number in unit

total_occur

NUMBER

Number of times line was executed

total_time

NUMBER

Total time spent executing line in nanoseconds

min_time

NUMBER

Minimum execution time for this line in nanoseconds

max_time

NUMBER

Maximum execution time for this line in nanoseconds

spare1

NUMBER

Unused

spare2

NUMBER

Unused

spare3

NUMBER

Unused

spare4

NUMBER

Unused

With Oracle database version 8.x, a sample textual report writer(profrep.sql) is provided with the PL/SQL demo scripts.

Security Model

The profiler only gathers data for units for which a user has CREATE privilege; you cannot use the package to profile units for which EXECUTE ONLY access has been granted. In general, if a user can debug a unit, the same user can profile it. However, a unit can be profiled whether or not it has been compiled DEBUG. Oracle advises that modules that are being profiled should be compiled DEBUG, since this provides additional information about the unit in the database.

Note:

DBMS_PROFILER treats any program unit that is compiled in NATIVE mode as if you do not have CREATE privilege, that is, you will not get any output.

Operational Notes

Typical Run

Improving application performance is an iterative process. Each iteration involves the following steps:

Running the application with one or more benchmark tests with profiler data collection enabled.

Analyzing the profiler data and identifying performance problems.

Fixing the problems.

The PL/SQL profiler supports this process using the concept of a "run". A run involves running the application through benchmark tests with profiler data collection enabled. You can control the beginning and the ending of a run by calling the START_PROFILER and STOP_PROFILER functions.

A typical run involves:

Starting profiler data collection in the run.

Executing PL/SQL code for which profiler and code coverage data is required.

Stopping profiler data collection, which writes the collected data for the run into database tables

Note:

The collected profiler data is not automatically stored when the user disconnects. You must issue an explicit call to the FLUSH_DATA or the STOP_PROFILER function to store the data at the end of the session. Stopping data collection stores the collected data.

As the application executes, profiler data is collected in memory data structures that last for the duration of the run. You can call the FLUSH_DATA function at intermediate points during the run to get incremental data and to free memory for allocated profiler data structures.

Flushing the collected data involves storing collected data in database tables. The tables should already exist in the profiler user's schema. The PROFTAB.SQL script creates the tables and other data structures required for persistently storing the profiler data.

Note that running PROFTAB.SQL drops the current tables. The PROFTAB.SQL script is in the RDBMS/ADMIN directory. Some PL/SQL operations, such as the first execution of a PL/SQL unit, may involve I/O to catalog tables to load the byte code for the PL/SQL unit being executed. Also, it may take some time executing package initialization code the first time a package procedure or function is called.

To avoid timing this overhead, "warmup" the database before collecting profile data. To do this, run the application once without gathering profiler data.

You can allow profiling across all users of a system, for example, to profile all users of a package, independent of who is using it. In such cases, the SYSADMIN should use a modified PROFLOAD.SQL script which:

Two Methods of Exception Generation

Each routine in this package has two versions that allow you to determine how errors are reported.

A function that returns success/failure as a status value and will never raise an exception

A procedure that returns normally if it succeeds and raises an exception if it fails

In each case, the parameters of the function and procedure are identical. Only the method by which errors are reported differs. If there is an error, there is a correspondence between the error codes that the functions return, and the exceptions that the procedures raise.

To avoid redundancy, the following section only provides details about the functional form.

Exceptions

Table 64-4

Exception

Description

version_mismatch

Corresponds to error_version.

profiler_error

Corresponds to either "error_param" or "error_io".

DBMS_PROFILER Exceptions

A 0 return value from any function denotes successful completion; a nonzero return value denotes an error condition. The possible errors are as follows:

'A subprogram was called with an incorrect parameter.'

error_param constant binary_integer := 1;

'Data flush operation failed. Check whether the profiler tables have been created, are accessible, and that there is adequate space.'

error_io constant binary_integer := 2;

There is a mismatch between package and database implementation. Oracle returns this error if an incorrect version of the DBMS_PROFILER package is installed, and if the version of the profiler package cannot work with this database version. The only recovery is to install the correct version of the package.

RESUME_PROFILER Function and Procedure

Syntax

START_PROFILER Functions and Procedures

This function starts profiler data collection in the user's session.

There are two overloaded forms of the START_PROFILER function; one returns the run number of the started run, as well as the result of the call. The other does not return the run number. The first form is intended for use with GUI-based tools controlling the profiler.